Styrene resins, particularly ABS resin have been widely used for various miscellaneous goods; interior and exterior materials for automobiles; housings and parts of electric appliances such as a rice cooker, electronic oven and vacuum cleaner; housings and parts of OA apparatuses such as phone and facsimile; and the like since they have excellent rigidity, impact resistance, heat deformation resistance, etc. Recently particularly with respect to interior and exterior materials for automobiles, there have been required characteristics such as dimensional stability at high temperature and moldability (surface appearance) and in addition, flexibility (low rigidity) necessary for enhancing safety at the time of collision as it can be seen in the side collision control according to Federal Motor Vehicle Safety Standard of the U.S.A.
Heretofore various approaches have been made to satisfy requirements for the mentioned characteristics, particularly flexibility (low rigidity) for enhancing safety and moldability (surface appearance) with respect to interior and exterior materials for automobiles. However materials having enough characteristics have not yet been obtained.
For example, JP-A-59-20346 discloses a process in which a specific plasticizer is added to a rubber-reinforced styrene resin. However the process is not satisfactory because heat deformation resistance is low and evaporation of the plasticizer occurs. Though use of a polypropylene resin comprising specific components has been studied, it has defects that surface appearance of a molded article is poor due to a sink mark, dimensional stability is not good due to warping and adhesivity to other material is poor.
With respect to a composition comprising ABS resin and acrylic acid ester copolymer, JP-A-58-179257 discloses that chemical resistance of a composition comprising a rubber-containing styrene resin and acrylic acid ester copolymer having a high gel content is enhanced, and JP-A-63-17954 discloses that chemical resistance of a composition comprising a rubber-containing maleimide-styrene copolymer, ABS resin and acrylic acid ester copolymer is enhanced. However in case of those compositions, surface appearance becomes poor, rigidity is high and stress at the time of impact is high, and thus there has not been obtained a composition having excellent surface appearance, flexibility and impact resistance and low stress and large energy absorption at the time of impact which are aimed at by the present invention.
Further the composition comprising a rubber-containing maleimide-styrene copolymer, ABS resin and acrylic acid ester copolymer, which is disclosed in JP-A-63-17954 has a problem that color shading occurs when a pigment is added thereto.
On the other hand, also with respect to a composition disclosed in JP-A-8-27336, comprising a rubber-containing maleimide-styrene copolymer, ABS resin and acrylic acid ester copolymer and having low stress and large energy absorption at the time of impact and excellent flexibility and impact strength, there have occurred a problem that surface appearance is poor (occurrence of flow mark).
An object of the present invention is to solve the mentioned problems and provide a thermoplastic resin composition having excellent moldability (surface appearance) and flowability; low rigidity such as bending strength and tensile strength; high impact resistance; low stress and large energy absorption at the time of impact; and high heat deformation resistance.